Vehicle relative-position calculation device and vehicle control device

ABSTRACT

This vehicle relative-position calculation device includes: a vehicle state information acquisition unit for acquiring state information of an own vehicle during traveling; a surrounding object information acquisition unit for acquiring information of a surrounding object around the own vehicle; a relative-position information conversion input unit to which relative-position information determined from the state information of the own vehicle and the information of the surrounding object, is inputted, and which converts the inputted relative-position information to relative-position information for which a specific position on the own vehicle is set as an origin; a position information storage unit which stores the relative-position information converted and a vehicle-fixed coordinate conversion unit to which the state information of the own vehicle acquired, is inputted, and which converts the relative-position information stored in the position information storage unit to present-time relative-position information, and outputs the present-time relative-position information to the position information storage unit.

TECHNICAL FIELD

The present disclosure relates to a vehicle relative-positioncalculation device and a vehicle control device.

BACKGROUND ART

Conventionally, it is known that the relative position between an ownvehicle and a surrounding object detected by the own vehicle is storedand the stored relative position of the surrounding object isrepresented as surrounding object position coordinates in avehicle-fixed coordinate system at the present time (for example, PatentDocument 1 below). Here, the rotation amount in the yaw direction andthe movement amounts in the front-rear direction and the lateraldirection of the own vehicle are calculated, and the surrounding objectposition coordinates are rotationally converted on the basis of therotation amount in the yaw direction of the own vehicle. From therotationally converted surrounding object position coordinates and themovement amounts of the own vehicle, the surrounding object positioncoordinates in the vehicle-fixed coordinate system are estimated. Here,for calculation of the movement amount in the lateral direction of theown vehicle, a sideslip angle of the own vehicle is taken intoconsideration, and the sideslip angle is calculated using a vehiclespeed, a steering angle, and a yaw rate.

CITATION LIST Patent Document

-   Patent Document 1: Japanese Laid-Open Patent Publication No.    2008-94213

Non-Patent Document

-   Non-Patent Document 1: Abe, Masato, “Automotive vehicle dynamics    theory and applications (2nd ed.)”, Tokyo Denki University Press,    pp. 64-65, January, 2012-   Non-Patent Document 2: C. M. Wang, “Location estimation and    uncertainty analysis for mobile robots,” IEEE, pp. 1230-1235, 1988

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in the method disclosed in Patent Document 1, when thesurrounding object position coordinates are rotationally converted onthe basis of the rotation amount in the yaw direction of the ownvehicle, sideslip is not taken into consideration, and therefore thereis a problem that the surrounding object position coordinates in thevehicle-fixed coordinate system cannot be estimated accurately. In acase of estimating a sideslip angle from a vehicle model using a vehiclespeed and a steering angle as inputs, since the sideslip angle iscalculated from the vehicle model using two inputs of the steering angleand the vehicle speed, the calculation is complicated, thus causing aproblem that offset error occurs due to integral processing through aprocess for calculating the sideslip angle and estimation error occursdue to modeling error of the vehicle model.

The present disclosure has been made to solve the above problem, and anobject of the present disclosure is to provide a vehiclerelative-position calculation device capable of accurately estimatingsurrounding object position coordinates in a vehicle-fixed coordinatesystem through simple calculation without being influenced by offseterror and vehicle modeling error.

Solution to the Problems

A vehicle relative-position calculation device according to the presentdisclosure includes: a vehicle state information acquisition unit foracquiring state information of an own vehicle during traveling; asurrounding object information acquisition unit for acquiringinformation of a surrounding object around the own vehicle; arelative-position information conversion input unit which is connectedto the vehicle state information acquisition unit and the surroundingobject information acquisition unit, and to which relative-positioninformation is inputted, the relative-position information beingrelative information of the surrounding object around the own vehiclerelative to the own vehicle determined from the state information of theown vehicle acquired by the vehicle state information acquisition unitand the information of the surrounding object acquired by thesurrounding object information acquisition unit, the relative-positioninformation conversion input unit being configured to convert theinputted relative-position information to relative-position informationfor which a specific position on the own vehicle is set as an origin; aposition information storage unit which is connected to therelative-position information conversion input unit and stores therelative-position information converted by the relative-positioninformation conversion input unit; and a vehicle-fixed coordinateconversion unit which is connected to the vehicle state informationacquisition unit and the position information storage unit and to whichthe state information of the own vehicle acquired by the vehicle stateinformation acquisition unit is inputted, the vehicle-fixed coordinateconversion unit being configured to convert the relative-positioninformation stored in the position information storage unit topresent-time relative-position information which is relative-positioninformation at a present time, and output the present-timerelative-position information to the position information storage unit.

Effect of the Invention

The vehicle relative-position calculation device according to thepresent disclosure makes it possible to accurately estimate surroundingobject position coordinates in a vehicle-fixed coordinate system at thepresent time through simple calculation without being influenced byoffset error and vehicle modeling error.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a vehicle controldevice according to embodiment 1.

FIG. 2 is a schematic system configuration diagram of a vehicle providedwith the vehicle control device according to embodiment 1.

FIG. 3 illustrates coordinate systems for explaining operation of thevehicle control device according to embodiment 1.

FIG. 4 illustrates steady-state circular turning at an extremely lowspeed of the vehicle provided with the vehicle control device accordingto embodiment 1.

FIG. 5 illustrates a case where a centrifugal force is not negligible insteady-state circular turning of the vehicle provided with the vehiclecontrol device according to embodiment 1.

FIG. 6 is a flowchart showing an operation procedure for the vehiclecontrol device according to embodiment 1.

FIG. 7 illustrates an example of a movement track of a surroundingobject stored in a vehicle relative-position calculation device of thevehicle control device according to embodiment 1.

FIG. 8 shows an example of hardware for signal processing in the vehiclerelative-position calculation device of the vehicle control deviceaccording to embodiment 1.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a preferred embodiment of a vehicle relative-positioncalculation device and a vehicle control device according to the presentdisclosure will be described with reference to the drawings. The presentembodiment generally relates to technology for estimating the relativeposition between an own vehicle and a surrounding object. In thedrawings, the same or corresponding parts are denoted by the samereference characters, to give description.

Embodiment 1

In the present embodiment, description will be given about a vehiclecontrol device which represents a preceding vehicle traveling in frontof an own vehicle and detected by the own vehicle, as a track in avehicle-fixed coordinate system at the present time, and controls thevehicle so as to follow the detected preceding vehicle.

FIG. 1 is a block diagram showing the schematic configuration of thevehicle control device according to embodiment 1. A vehiclerelative-position calculation device 210 according to the presentembodiment is provided to a vehicle control device 200, and includes avehicle state information acquisition unit 211, a surrounding objectinformation acquisition unit 212, a vehicle-fixed coordinate conversionunit 213, a position information storage unit 214, a relative-positioninformation conversion input unit 215, and a relative-positioninformation conversion output unit 216.

The vehicle control device 200 is a device for controlling the vehicle,and is composed of a ROM and a RAM for storing various programs, and aCPU for executing the programs. The vehicle control device 200 is, forexample, an advanced driver assistance system electronic control unit(ADAS-ECU).

In the vehicle relative-position calculation device 210 of the presentembodiment, the relative-position information conversion input unit 215performs relative position conversion for obtaining the relativeposition between the own vehicle and a surrounding object on the basisof the vehicle state of the own vehicle acquired by the vehicle stateinformation acquisition unit 211 and surrounding object positioninformation acquired by the surrounding object information acquisitionunit 212, and performs coordinate conversion for the surrounding objectposition information acquired by the surrounding object informationacquisition unit 212, with the origin set as a point where the sideslipangle of the vehicle is zero. The relative-position informationconversion input unit 215 outputs the obtained result to the positioninformation storage unit 214. The vehicle-fixed coordinate conversionunit 213 performs coordinate conversion for surrounding object positioninformation stored in the position information storage unit 214, into avehicle-fixed coordinate system, on the basis of the own-vehicle stateacquired from the vehicle state information acquisition unit 211. Theposition information storage unit 214 performs also update of trackinformation of the stored surrounding object positions. Therelative-position information conversion output unit 216 performsconversion for the surrounding object position information stored in theposition information storage unit 214, on the basis of a relativeposition conversion value calculated by the relative-positioninformation conversion input unit 215 and a predetermined valuedetermined depending on a location set as an origin for the surroundingobject position information.

In addition, a vehicle control unit 220 is provided to the vehiclecontrol device 200. The vehicle control unit 220 calculates a targetvalue to be outputted to an actuator control unit 300, on the basis ofthe own-vehicle state and the surrounding object position informationaround the own vehicle calculated by the vehicle relative-positioncalculation device, and outputs the target value to the actuator controlunit 300.

In addition, for the vehicle control device 200, a vehicle stateinformation detection unit 110 and a surrounding object informationdetection unit 120 are provided as external input devices. Here, thevehicle state information detection unit 110 is a detection unit fordetecting information about the own vehicle, and includes, for example,a vehicle speed sensor and a yaw rate sensor. The information detectedby the vehicle state information detection unit 110 is acquired by thevehicle state information acquisition unit 211 provided to the vehiclerelative-position calculation device 210.

The surrounding object information detection unit 120 is a detectionunit for detecting information including the position of the surroundingobject, and is, for example, a front camera. Alternatively, a lightdetection and ranging (LiDAR) device, a laser, a sonar, avehicle-to-vehicle communication device, or a road-to-vehiclecommunication device is applicable. The information detected by thesurrounding object information detection unit 120 is acquired by thesurrounding object information acquisition unit 212 provided to thevehicle relative-position calculation device 210.

In addition, for the vehicle control device 200, the actuator controlunit 300 is provided as an external device. The actuator control unit300 is a control unit for performing control so that an actuatorachieves the target value, and is, for example, an electric powersteering ECU. Alternatively, a powertrain ECU or a brake ECU isapplicable.

FIG. 2 is a system configuration diagram showing the schematicconfiguration of the vehicle provided with the vehicle control deviceaccording to embodiment 1. In FIG. 2 , the vehicle 1 includes a steeringwheel 2, a steering shaft 3, a steering unit 4, an electric powersteering unit 5, a powertrain unit 6, a brake unit 7, a yaw rate sensor111, a vehicle speed sensor 112, a front camera 121, the vehicle controldevice 200, an electric power steering controller 310, a powertraincontroller 320, and a brake controller 330.

The steering wheel 2 provided for a driver to operate the vehicle 1 isjoined to the steering shaft 3. The steering unit 4 is connected to thesteering shaft 3. The steering unit 4 rotatably supports front wheelswhich are steered wheels, and is turnably supported by a vehicle bodyframe.

Therefore, torque generated through operation of the steering wheel 2 bythe driver rotates the steering shaft 3, to turn the front wheels in theleft-right direction by the steering unit 4. Thus, the driver canoperate the lateral movement amount of the vehicle when the vehiclemoves frontward/backward. The steering shaft 3 can also be rotated bythe electric power steering unit 5, and through a command to theelectric power steering controller 310, the front wheels can be freelyturned independently of operation of the steering wheel 2 by the driver.

The vehicle control device 200 is configured by an integrated circuitsuch as a microprocessor, and includes an A/D conversion circuit, a D/Aconversion circuit, a CPU, a ROM, a RAM, and the like. The yaw ratesensor 111 for detecting the yaw rate of the vehicle 1, the vehiclespeed sensor 112 for detecting the speed of the vehicle 1, the frontcamera 121, the electric power steering controller 310, the powertraincontroller 320, and the brake controller 330 are connected to thevehicle control device 200.

The vehicle control device 200 processes information inputted from theconnected sensors in accordance with a program stored in the ROM,transmits a target steering angle to the electric power steeringcontroller 310, transmits a target drive force to the powertraincontroller 320, and transmits a target braking force to the brakecontroller 330. In a case where acceleration/deceleration control is notperformed by the vehicle control device 200, the powertrain controller320 and the brake controller 330 need not be connected to the vehiclecontrol device 200.

The front camera 121 is provided at a position where the front camera121 can detect marking lines in front of the vehicle as an image, anddetects information of a surrounding object frontward of the ownvehicle, such as lane information or the position of an obstacle, on thebasis of the image information. Although only the camera for detecting afrontward surrounding object is shown as an example in the presentembodiment, a camera for detecting a rearward or lateral surroundingobject may be provided.

The electric power steering controller 310 controls the electric powersteering unit 5 so as to achieve the target steering angle transmittedfrom the vehicle control device 200. The powertrain controller 320controls the powertrain unit 6 so as to achieve the target drive forcetransmitted from the vehicle control device 200. In a case where thedriver performs speed control, the powertrain unit 6 is controlled onthe basis of the amount of tread on an accelerator pedal.

Although the vehicle using only an engine as a drive force source isshown as an example in the present embodiment, a vehicle using only anelectric motor as a drive force source, a vehicle using both an engineand an electric motor as a drive force source, or the like is alsoapplicable.

The brake controller 330 controls the brake unit 7 so as to achieve thetarget braking force transmitted from the vehicle control device 200. Ina case where the driver performs speed control, the brake unit 7 iscontrolled on the basis of the amount of tread on a brake pedal.

Hereinafter, actual operation of the above vehicle control device 200will be described in more detail with reference to the drawings.

FIG. 3 is a diagram showing coordinate systems used for explanationtherefor. Here, as sub-coordinate systems for the vehicle-fixedcoordinate system, the following three kinds of coordinate systems aredefined, and description will be given using these coordinate systems.In the drawings, a coordinate system represented by X₀, Y₀ is a cameracoordinate system with an origin O_(CAM) set at a detection referenceposition of the front camera 121 attached on the center axis of thevehicle 1 indicated by a dotted line. A coordinate system represented byX₁, Y₁ is a yaw rotation center coordinate system with an origin O_(β=0)set at a position where the sideslip angle is zero on the center axis ofthe vehicle 1. A coordinate system represented by X₂, Y₂ is a bumpercoordinate system with an origin O_(BUM) set at a bumper position on thecenter axis of the vehicle 1.

In the description below, the following notations are used regardingthese plurality of coordinate systems. For example, a position vector isdenoted by PCAM_p in the camera coordinate system, by PYAW_p in the yawrotation center coordinate system, and by PBUM_p in the bumpercoordinate system. That is, three characters as abbreviation of thecorresponding coordinate system are written before a symbol p of aposition vector. It is noted that a character written in an italicformat (here, p) indicates that this is a vector.

FIG. 4 shows a scene of steady-state circular turning at an extremelylow speed of the vehicle 1 in embodiment 1. In FIG. 4 , a precedingvehicle 10 is traveling in front of the vehicle 1, and the front camera121 detects the relative position between the preceding vehicle 10 andthe vehicle 1. The detected relative position is PCAM_p_(t)=[x_(t),y_(t), 1]^(T) (here, “t” denotes the time when the detection isperformed and “T” is a symbol indicating a transposed matrix;hereinafter, the same applies). When the vehicle 1 is at an extremelylow speed, no centrifugal force acts on the vehicle. Therefore,steady-state circular turning is performed in a geometrical relationshipof Ackermann steering geometry (in this case, the rotation centers ofthe four wheels on the front and rear sides are at one identical pointOc), and there is no sideslip angle at the rear shaft center.Accordingly, here, the rear shaft center is set as the origin O_(β=0) ofthe yaw rotation center coordinate system.

In FIG. 4 , l_(cr) denotes a distance from the detection referenceposition of the front camera 121 to the rear shaft center, and x_(t) andy_(t) respectively denote distances in an X direction (the advancingdirection of the own vehicle at the point O_(CAM)) and a Y direction(the direction orthogonal to the X direction) from the detectionreference position of the front camera 121 to the position (see abovePCAM_p_(t)) where the preceding vehicle 10 is detected.

Next, FIG. 5 shows a case of such a vehicle speed that the centrifugalforce of steady-state circular turning is not negligible, unlike theextremely low vehicle speed. As the vehicle speed increases, theposition O_(β=0) where the sideslip angle is zero on the vehicle centeraxis moves frontward from the rear shaft center.

Here, a turning radius R of steady-state circular turning of the centerof gravity and a sideslip angle β can be calculated by Expression (1)and Expression (2) from a vehicle weight m, a front shaft-gravity centerdistance l_(f), a rear shaft-gravity center distance l_(r), a wheelbasel_(w), front wheel cornering power K_(f), rear wheel cornering powerK_(r), a vehicle speed ν, and a steering angle δ (see, for example,Expression 3.29 and Expression 3.31 in Non-Patent Document 1).

[Mathematical1] $\begin{matrix}{R = {( {1 - {\frac{m( {{l_{f}K_{f}} - {l_{r}K_{r}}} )}{2l_{w}^{2}K_{f}K_{r}}v^{2}}} )\frac{l_{w}}{\delta}}} & (1)\end{matrix}$ [Mathematical2] $\begin{matrix}{\beta = {( \frac{l_{r} - {\frac{ml_{f}}{2l_{w}K_{r}}v^{2}}}{1 - {\frac{m( {{l_{f}K_{f}} - {l_{r}K_{r}}} )}{2l_{w}^{2}K_{f}K_{r}}v_{2}}} )\frac{\delta}{l_{w}}}} & (2)\end{matrix}$

From Expression (1) and Expression (2), L_(β=0) which is the distancefrom the center of gravity to the position where the sideslip angle iszero on the vehicle body center axis, is represented by Expression (3).

[Mathematical3] $\begin{matrix}{L_{\beta = 0} = {{{R\sin\beta} \approx {R\beta}} = ( {l_{r} - {\frac{ml_{f}}{2l_{w}K_{r}}v^{2}}} )}} & (3)\end{matrix}$

Using Expression (3), where the distance from the detection referenceposition of the front camera 121 to the rear shaft center is denoted byl_(cr), a distance L_(c) from the origin O_(CAM) of the cameracoordinate system to the origin O_(β=0) of the yaw rotation centercoordinate system is represented by Expression (4).

[Mathematical4] $\begin{matrix}{L_{c} = ( {l_{cr} - {\frac{ml_{f}}{2l_{w}K_{r}}v^{2}}} )} & (4)\end{matrix}$

Hereinafter, the distance L_(c) may be referred to as a relativeposition conversion value.

In a case where the vehicle 1 is performing steady-state circularturning, the position of the preceding vehicle at time t is denoted byPCAM_p_(t), and at time t, a position PCAM_p_(t-1) of the precedingvehicle at time t-1 is considered. Here, PCAM_p is in the cameracoordinate system. On the other hand, the yaw rate detected on thevehicle 1 is in the yaw rotation center coordinate system.

Therefore, considering a yaw angular momentum and a movement amount ofthe vehicle 1 during a control cycle from time t-1 to time t, theposition PCAM_p_(t-1) of the preceding vehicle in the camera coordinatesystem at time t-1 can be converted into the yaw rotation centercoordinate system at the present time t, by performing coordinateconversion for the PCAM_p_(t-1) into the yaw rotation center coordinatesystem at the present time t-1 and then performing calculation forreflecting the yaw angular momentum and the movement amount during thecontrol cycle of the vehicle 1. Then, the calculated value can beconverted into the camera coordinate system at time t, by furtherperforming coordinate conversion from the yaw rotation center coordinatesystem to the camera coordinate system.

For the coordinate conversion, the relative position conversion valueL_(c) that can be calculated by Expression (4) is used. The precedingvehicle position PYAW_p in the yaw rotation center coordinate system isin a coordinate system where the sideslip angle is zero.

In the calculation for the relative position conversion value L_(c), thevehicle speed ν is used as one input, and the vehicle weight m, thefront shaft-gravity center distance l_(f), the wheelbase l_(w), and therear wheel cornering power K_(r) are parameters that can be defined inadvance for each vehicle. Therefore, the calculation is easy. Inaddition, since the number of parameters defined in advance is small,modeling error is less likely to occur. In addition, since integral isnot included in the calculation, offset error does not occur.

With respect to the position PCAM_p_(t) of the preceding vehiclesequentially detected by the front camera, the movement amount of theown vehicle is sequentially calculated through the above method, wherebyit is possible to accurately express the position of the precedingvehicle in the vehicle-fixed coordinate system as a track.

FIG. 6 is a flowchart showing an operation procedure in the vehiclecontrol device of embodiment 1. With reference to the flowchart,operation for one control cycle described below in the vehicle controldevice will be described. In the actual device, the series of operationsis repeated for necessary control cycles. For clarifying this, thelowermost stage in the flowchart is indicated as not “END” but “RETURN”which is normally used in indication of a sub-flowchart.

First, in step S100 in the entire process shown in FIG. 6 , the vehiclestate information acquisition unit acquires vehicle state information.The vehicle state information is information such as the yaw rate andthe speed of the own vehicle. In the present embodiment, the yaw rate γand the vehicle speed ν are acquired.

In the next step S110, the vehicle-fixed coordinate conversion unitcalculates a surrounding object position PYAW_cp_(k) in the yaw rotationcenter coordinate system at the present time, on the basis of themovement amount and the yaw-direction rotation amount of the own vehiclefrom the previous control cycle and the track of surrounding objectpositions PYAW_p_(k) (k=1, . . . , N) in the yaw rotation centercoordinate system stored in the position information storage unit.

In the present embodiment, a movement amount [sx, sy]^(T) of the ownvehicle is approximated by an arc, and is calculated by Expression (5)using the vehicle speed ν and the yaw rate γ acquired in step S100 and acontrol cycle dt (see, for example, Non-Patent Document 2). The controlcycle dt is the calculation cycle of the entire flowchart in FIG. 6 ,and is, for example, 100 ms.

[Mathematical5] $\begin{matrix}{\begin{bmatrix}{sx} \\{sy}\end{bmatrix} = {\begin{bmatrix}{\cos( \frac{\gamma{dt}}{2} )} \\{\sin( \frac{\gamma{dt}}{2} )}\end{bmatrix}\lbrack {{vdt}\sin{c( \frac{\gamma{dt}}{2} )}} \rbrack}} & (5)\end{matrix}$

If γdt is sufficiently small, Expression (6) may be used instead.

[Mathematical6] $\begin{matrix}{\begin{bmatrix}{sx} \\{sy}\end{bmatrix} \approx {\begin{bmatrix}{\cos( \frac{\gamma{dt}}{2} )} \\{\sin( \frac{\gamma{dt}}{2} )}\end{bmatrix}\lbrack{vdt}\rbrack}} & (6)\end{matrix}$

A matrix for conversion to the present time in the yaw rotation centercoordinate system is set as shown in Expression (7) on the basis of themovement amount [sx, sy]^(T) of the own vehicle, the yaw rate γ acquiredin step S100, and the control cycle dt.

[Mathematical7] $\begin{matrix}{{PYAW\_ T}_{DR} = \begin{bmatrix}{\cos( {{- \gamma}{dt}} )} & {- {\sin( {{- \gamma}{dt}} )}} & {- {sx}} \\{\sin( {{- \gamma}{dt}} )} & {\cos( {{- \gamma}{dt}} )} & {sy} \\0 & 0 & 1\end{bmatrix}} & (7)\end{matrix}$

Next, the surrounding object position PYAW_cp_(k) (k=1, N) at thepresent time in the yaw rotation center coordinate system is calculatedby Expression (8). [Mathematical 8]

PYAW_cp _(k)(k=1, . . . ,N)=PYAW_T _(DR)PYAW_p _(k)(k=1, . . . ,N)  (8)

In the next step S120, the surrounding object information acquisitionunit acquires the surrounding object information. The surrounding objectinformation is information including the position of the surroundingobject. In the present embodiment, the position PCAM_p_(t)=[x_(t),y_(t), 1]^(T) of the preceding vehicle to be followed by the own vehicleat the present time t is acquired.

In the next step S130, the relative-position information conversioninput unit calculates the relative position conversion value, andconverts the surrounding object information acquired in step S120, intothe yaw rotation center reference coordinate system. In the presentembodiment, the relative position conversion value L_(c) is calculatedusing Expression (4) from the vehicle weight m, the front shaft-gravitycenter distance l_(f), the wheelbase l_(w), and the rear wheel corneringpower K_(r) set in advance for the vehicle and the vehicle speed νacquired in step S100.

A matrix for conversion to the yaw rotation center reference coordinatesystem is set as shown in the following Expression (9) on the basis ofthe relative position conversion value L_(c).

[Mathematical9] $\begin{matrix}{{PYAW\_ T}_{CAM} = \begin{bmatrix}1 & 0 & L_{c} \\0 & 1 & 0 \\0 & 0 & 1\end{bmatrix}} & (9)\end{matrix}$

A surrounding object position PYAW_p_(t) in the yaw rotation centercoordinate system is calculated by the following Expression (10) usingthe conversion matrix PYAW_T_(CAM) set in the above Expression (9).

[Mathematical 10]

PYAW_p _(t)=PYAW_T _(CAM)PCAM_p _(t)  (10)

In the next step S140, the position information storage unit performsupdate of track information of the surrounding object positions storedtherein. The surrounding object position PYAW_p_(t) calculated in stepS130 is added as a latest value, and among the surrounding objectpositions PYAW_cp_(k) (k=1, . . . , N) at the present time updated instep S110, the surrounding object position PYAW_cp_(N) for the oldesttime is deleted, as shown in Expression (11).

[Mathematical11] $\begin{matrix} \begin{matrix}{{PYAW\_ p}_{1} = {PYAW\_ p}_{t}} \\{{PYAW\_ p}_{2} = {PYAW\_ cp}_{1}} \\\begin{matrix} & & & \vdots & & & & & & & \vdots \end{matrix} \\{{PYAW\_ p}_{N - 1} = {PYAW\_ cp}_{N - 2}} \\{{PYAW\_ p}_{N} = {PYAW\_ cp}_{N - 1}}\end{matrix} \} & (11)\end{matrix}$

In the next step S150, the relative-position information conversioninput unit converts the track information of the surrounding objectpositions stored in the position information storage unit, into thebumper coordinate system. In the present embodiment, a matrix forconversion to the bumper coordinate system is set as shown in Expression(12) on the basis of the relative position conversion value L_(c)calculated in step S130 and the distance l_(bc) between the origin ofthe bumper coordinate system and the origin of the camera coordinatesystem.

[Mathematical12] $\begin{matrix}{{PBUM\_ T}_{YAW} = \begin{bmatrix}1 & 0 & {- ( {L_{C} + l_{bc}} )} \\0 & 1 & 0 \\0 & 0 & 1\end{bmatrix}} & (12)\end{matrix}$

A track PBUM_p_(k) (k=1, . . . , N) of the surrounding object positionin the bumper coordinate system is calculated by Expression (13).

[Mathematical 13]

PBUM_p _(k)=PBUM_T _(YAW)PYAW_p _(k)(k=1, . . . ,N)  (13)

Here, by optionally changing the conversion matrix, it is possible toset any position as an origin for the track information of thesurrounding object positions stored in the position information storageunit. For example, in a case of desiring conversion to the cameracoordinate system, the conversion matrix may be set as shown inExpression (14) and calculation may be performed as shown in Expression(15).

[Mathematical14] $\begin{matrix}{{PCAM\_ T}_{YAW} = \begin{bmatrix}1 & 0 & {- L_{C}} \\0 & 1 & 0 \\0 & 0 & 1\end{bmatrix}} & (14)\end{matrix}$ [Mathematical15] $\begin{matrix}{{PCAM\_ p}_{k} = {{PCAM\_ T}_{YAW}{PYAW\_ p}_{k}( {{k = 1},\ldots,N} )}} & (15)\end{matrix}$

In the next step S160, a target steering angle for following thepreceding vehicle is calculated on the basis of the track of thesurrounding object positions calculated in step S150.

In the last step S170, the actuator control unit controls the actuatorso as to achieve the target value. In the present embodiment, steeringcontrol is assumed and control is performed using known technology suchas PID control in the electric power steering unit so as to achieve thetarget steering angle.

FIG. 7 shows a track of surrounding object positions stored in theposition information storage unit when the vehicle is controlled so asto follow the preceding vehicle under application of the vehiclerelative-position calculation device in the present embodiment describedwith reference to FIG. 6 . A set of points indicated by PYAW_p_(k) (k=1,. . . , N) represents a track through which the preceding vehicle hastraveled.

With the above configuration, it is possible to accurately estimate thepast surrounding object positions through simple calculation withoutbeing influenced by offset error and modeling error. Thus, a track canbe obtained with high accuracy, whereby control that enables the ownvehicle to accurately follow the preceding vehicle can be achieved.

In addition, the relative-position information conversion input unit isprovided for converting surrounding object position information storedin the position information storage unit to a relative-value positionfor which any point on the own vehicle is set as an origin. Thus, thesurrounding object position can be changed to surrounding objectposition information for which any point on the vehicle is set as anorigin. For example, in a case where a vehicle control device forperforming control in a camera coordinate system is provided, byconverting surrounding object position information into a cameracoordinate system and then outputting the converted information, itbecomes possible to use highly accurate surrounding object positioninformation for which the control system of the vehicle control deviceneed not be changed.

Further, with the configuration of the vehicle control device having theabove vehicle relative-position calculation device and the vehiclecontrol unit, past surrounding object positions can be obtained withhigh accuracy, whereby performance of control for the vehicle behavioris improved. Specifically, it becomes possible to improve follow-upperformance in vehicle control for following the preceding vehicle oraccurately perform obstacle avoidance in vehicle control for avoiding anobstacle.

FIG. 8 shows an example of hardware 30 for the signal processing in thevehicle relative-position calculation device according to the presentdisclosure. As shown in FIG. 8 , the hardware 30 for the signalprocessing in this device includes a processor 31 and a storage device32. The storage device 32 is provided with a volatile storage devicesuch as a random access memory and a nonvolatile auxiliary storagedevice such as a flash memory (which are not shown). Instead of a flashmemory, an auxiliary storage device of a hard disk may be provided. Theprocessor 31 executes a program inputted from the storage device 32. Inthis case, the program is inputted from the auxiliary storage device tothe processor 31 via the volatile storage device. The processor 31 mayoutput data such as a calculation result to the volatile storage deviceof the storage device 32, or may store such data into the auxiliarystorage device via the volatile storage device.

The contents described in the above embodiment are merely examples andthe present disclosure is not limited thereto. For example, theconfiguration in which the position of the surrounding object around theown vehicle is represented in the vehicle-fixed coordinate at thepresent time, to perform vehicle control, is also applicable to variouscases other than the present embodiment. For example, this configurationis applicable to a vehicle control device for detecting an obstacle as asurrounding object and controlling a vehicle so as to avoid the obstacleor to stop, or a vehicle control device for detecting a white line on aroad as a surrounding object and controlling a vehicle so as to travelalong the white line. A person skilled in the art can implement thevehicle relative-position calculation device and the vehicle controldevice according to the present embodiment in other various mannerswithout deviating from the gist of the present embodiment.

DESCRIPTION OF THE REFERENCE CHARACTERS

-   -   1 vehicle    -   2 steering wheel    -   3 steering shaft    -   4 steering unit    -   5 electric power steering unit    -   6 powertrain unit    -   7 brake unit    -   10 preceding vehicle    -   111 yaw rate sensor    -   112 vehicle speed sensor    -   121 front camera    -   200 vehicle control device    -   210 vehicle relative-position calculation device    -   211 vehicle state information acquisition unit    -   212 surrounding object information acquisition unit    -   213 vehicle-fixed coordinate conversion unit    -   214 position information storage unit    -   215 relative-position information conversion input unit    -   216 relative-position information conversion output unit    -   220 vehicle control unit    -   300 actuator control unit    -   310 electric power steering controller    -   320 powertrain unit    -   330 brake controller

1. A vehicle relative-position calculation device comprising: a vehiclestate information acquisition circuitry to acquire state information ofan own vehicle during traveling; a surrounding object informationacquisition circuitry to acquire information of a surrounding objectaround the own vehicle; a relative-position information conversion inputcircuitry which is connected to the vehicle state informationacquisition circuitry and the surrounding object information acquisitioncircuitry, and to which relative-position information is inputted, therelative-position information being relative information of thesurrounding object around the own vehicle relative to the own vehicledetermined from the state information of the own vehicle acquired by thevehicle state information acquisition circuitry and the information ofthe surrounding object acquired by the surrounding object informationacquisition circuitry, the relative-position information conversioninput circuitry being configured to convert the inputtedrelative-position information to relative-position information for whicha specific position on the own vehicle is set as an origin; a positioninformation storage device which is connected to the relative-positioninformation conversion input circuitry and stores the relative-positioninformation converted by the relative-position information conversioninput circuitry; and a vehicle-fixed coordinate conversion circuitrywhich is connected to the vehicle state information acquisitioncircuitry and the position information storage device and to which thestate information of the own vehicle acquired by the vehicle stateinformation acquisition circuitry is inputted, the vehicle-fixedcoordinate conversion circuitry being configured to convert therelative-position information stored in the position information storagedevice to present-time relative-position information which isrelative-position information at a present time, and output thepresent-time relative-position information to the position informationstorage device.
 2. The vehicle relative-position calculation deviceaccording to claim 1, wherein the specific position is a position wherea sideslip angle of the own vehicle is zero.
 3. The vehiclerelative-position calculation device according to claim 1, furthercomprising a relative-position information conversion output circuitrywhich converts the present-time relative-position information outputtedfrom the vehicle-fixed coordinate conversion circuitry and stored in theposition information storage device, to present-time positioninformation for which a predetermined position on the own vehicle is setas an origin.
 4. A vehicle control device comprising: the vehiclerelative-position calculation device according to claim 1; and a vehiclecontrol circuitry to control a behavior of the own vehicle on the basisof the present-time relative-position information and the stateinformation of the own vehicle obtained by the vehicle relative-positioncalculation device.
 5. The vehicle relative-position calculation deviceaccording to claim 2, further comprising a relative-position informationconversion output circuitry which converts the present-timerelative-position information outputted from the vehicle-fixedcoordinate conversion circuitry and stored in the position informationstorage device, to present-time position information for which apredetermined position on the own vehicle is set as an origin.
 6. Avehicle control device comprising: the vehicle relative-positioncalculation device according to claim 2; and a vehicle control circuitryto control a behavior of the own vehicle on the basis of thepresent-time relative-position information and the state information ofthe own vehicle obtained by the vehicle relative-position calculationdevice.
 7. A vehicle control device comprising: the vehiclerelative-position calculation device according to claim 3; and a vehiclecontrol circuitry to control a behavior of the own vehicle on the basisof the present-time relative-position information and the stateinformation of the own vehicle obtained by the vehicle relative-positioncalculation device.